CHIRAL ACYLSILANES IN ORGANIC-SYNTHESIS .3. SILICON-DIRECTED STEREOSELECTIVE PREPARATION AND IRELAND ESTER ENOLATE REARRANGEMENT OF O-ACYL-SUBSTITUTED ALPHA-SILYLATED ALLYL ALCOHOLS

Stereocontrolled addition of alk-1-enylmetal reagents to the chiral (a lkoxymethyl)-substituted acylsilanes (+/-)-6 gave rise to alpha-silyla ted allyl alcohols, which were converted to the corresponding acetates or propionates 11-16 (Scheme 2). Deprotonation and silylation with Me (3)SiCl afforded - in an Ireland ester-enolate-accelerated Claisen rea rrangement - stereoselectively alpha,delta-silylated gamma,delta-unsat urated carboxylic acids 18-24 (Scheme 4). The Me(3)Si groups in alpha- position to the COOH group of these compounds were removed chemoselect ively in presence of the chiral silyl group in delta-position by treat ment with Bu(4)NF . 3 H2O or Et(3)N . 3 HF (-->27-32; Scheme 5). The r eaction sequence allows a novel stereocontrolled access to chiral C-fr ameworks possessing a vinylsilane moiety with its full reaction potent ial.